Is there a universal diet that can add benefits to boost the effectiveness of cancer treatments? The short answer is no, according to an interesting 2020 review of published research on dietary interventions and cancer. Instead of a single dietary plan for all cancers, it appears that a number of diets are better for some cancers than for others! The authors explored several types of cancer and the eating plans that seemed to reinforce good treatment results:

• Plant-based diets were beneficial for prostate cancer (PCa) patients, as was increased intake of omega-3 fatty acids
• Ketogenic diets were helpful for those with malignant gliomas (brain and spinal cord cancers)
• High fiber diets were associated with better results for colorectal cancer patients as well as cancer patients on immunotherapy.^[i]

Our own blog posts contain numerous topics on nutrition and PCa, with an increasing trend toward the benefits of plant-based eating. As cited by the authors above, plant-based diets along with omega-3 fatty acids have been linked with better PCa treatment outcomes.

However, it’s not as simple as it looks. If we dig more deeply into studies, we start to see things that appear contradictory. For example, the relationship between dairy products and PCa risk remains controversial. A 2019 study concluded, “Our findings do not support the previously reported harmful impact of dairy consumption on overall prostate cancer risk among men in the United States.”^[ii] However, a 2022 large-scale study with an average follow-up of nearly 8 years found that the more dairy consumed, the greater the risk for PCa.^[iii]

There’s also disagreement about dietary fat consumption and PCa risk. Some laboratory animal studies suggest that diets high in fat promote tumor growth, but note that the animal feed included a high percentage of corn oil as dietary fat. Corn oil—widely used in Western diets and processed foods—has been linked with greater risk of breast cancer;^[iv] though plant-based, its molecular components may actually foster certain metabolic processes linked to cancer cell activity. Curiously, recent studies that evaluate the effects of ketogenic diets (very low carbohydrate, low protein, high fat) have found that contrary to low fat diets, those in which animal fat such as lard or milk fat were the primary source of calories produced slower tumor growth in mice implanted with PCa. The exact mechanisms by which ketogenic diets discourage PCa growth are not known, but main theories point to downregulating cancer-signaling molecular pathways, and reducing the amount of available blood sugar needed by tumors for their growth.

Low fat or high fat? Contradictory study results are confusing, resulting in a PCa dietary dilemma: Should I eat a low fat plant-based diet, or a low carbohydrate diet high in animal fat? The answer simply isn’t clear, since we are still learning much about differences in PCa cell lines at the genomic level, cultural and geographic factors (e.g., some population groups in south Asia consume high amounts of whole milk yet have some of the lowest PCa rates in the world), and the biological and metabolic processes by which food ingredients may switch tumor-promoting genes on or off.

Thus, there does not seem to be a one-diet-fits-all for PCa patients who have been treated or are in treatment/Active Surveillance for their disease. We suggest a few guiding principles:

1. Talk to the doctor who knows you best, usually your primary care (PC) physician who has access to your medical history. He/she may be able to help you understand how your body metabolizes food, and dietary habits best suited to your overall health.
2. Don’t panic over contradictory research results. Use common sense while continuing to learn.
3. Whatever the proportion of carbohydrates to fats in your own diet, remember that the Western diet is full of unhealthy processed carbs that bring on abnormal cell behavior. Eat unprocessed or minimally processed whole grains, vegetables, fruits and beans—all of which are plant-based.
4. If you consume animal fat and protein, aim for organically sourced meat and dairy to minimize the risk of exposure to antibiotics, hormones, and herbicides/pesticides hidden in the feed given to the animals.

Until the mysteries of PCa are unraveled, researchers are striving valiantly to understand how diet can promote better treatment outcomes. Conflicting study results can be frustrating, but the preponderance of research evidence still points to plant-forward diets. We will continue to post blogs based on new study results as they become available, so keep tuning in to our blog.

NOTE: This content is solely for purposes of information and does not substitute for diagnostic or medical advice. Talk to your doctor if you are experiencing pelvic pain, or have any other health concerns or questions of a personal medical nature.

References

[i] Mann S DO, Sidhu M DO, Gowin K DO. Understanding the Mechanisms of Diet and Outcomes in Colon, Prostate, and Breast Cancer; Malignant Gliomas; and Cancer Patients on Immunotherapy. Nutrients. 2020 Jul 26; 12(8): 2226.
[ii] Preble I, Zhang Z, Kopp R, Garzotto M, Bobe G, Shannon J, Takata Y. Dairy Product Consumption and Prostate Cancer Risk in the United States. Nutrients. 2019 Jul 16;11(7):1615.
[iii] Orlich MJ, Mashchak AD, Jaceldo-Siegl K, Utt JT et al. Dairy foods, calcium intakes, and risk of incident prostate cancer in Adventist Health Study-2. Am J Clin Nutr. 2022 Jun 8:nqac093.
[iv] Escrich R, Costa I, Moreno M, Cubedo M et al.A high-corn-oil diet strongly stimulates mammary carcinogenesis, while a high-extra-virgin-olive-oil diet has a weak effect, through changes in metabolism, immune system function and proliferation/apoptosis pathways. J Nutr Biochem. 2019;64:218-277.